In general, a toner cartridge (a developer cartridge) is detachably mounted in a main frame of an image forming device, such as a copier and a laser printer, in order to supply toner to a developing device. Such a developer cartridge includes a toner chamber formed with an opening for supplying toner to the developing device, a shutter movable between an open position and a closed position, and a lock mechanism to lock the shutter at the closed position.
It has been conventionally known a developer cartridge having a lock mechanism to lock a shutter with a movable lock pin provided in a toner container. The lock pin is engageable with a through-hole formed on a side wall of the shutter so as to lock the shutter. In this lock mechanism, an unlock pin is provided in a main frame of an image forming device. When the developer cartridge is mounted in the main frame, the unlock pin is inserted into the through-hole to push the lock pin out of the through-hole to unlock the shutter. In association with rotation of the toner container, the shutter is relatively open. Therefore, the toner can be supplied from an opening formed in the toner container.